The distribution of hydrogen isotopes is important for understanding plasma-first wall interaction in fusion reactors i.e. ITER where especially the tritium retention in the plasma facing walls is a key parameter both for safety as well as economy [1]. Measuring the hydrogen content and obtaining spatial distribution is also of a general interest in material science, since the presence of hydrogen may significantly influence the physical and chemical properties of a material.
Common methods to determine hydrogen contents based on Ion Beam Analysis (IBA) techniques are Elastic Recoil Detection (ERDA) and Nuclear Reaction Analysis (NRA). The main advantage of these methods are negligible induced damage and easy sample handling. Furthermore IBA techniques combined with a microprobe, capable of forming µm beam spot and lateral scanning, makes 3D elemental profiling feasible [2].
At the Uppsala Tandem Laboratory we have recently started to use our microprobe for such mapping of specifically hydrogen isotope distributions. The access to ions heavier then helium at our accelerator facility has given us a flexibility to optimize the ion beam parameters related to a specific sample of interest.
To evaluate the potential of our microprobe setup, such as sensitivity and spatial resolution, we have studied depth profiles as well as lateral images of implanted H and D in elements suggested as wall components inside fusion reactors namely Be, C and W. ERDA with a stopping foil, using both 4He ion beams as well as heavier ion species such as 12C, was conducted in this first pilot study to confirm the instrumental performance. Hydrogen isotopes have also been detected using NRA reactions such as D[3He,p]4He and D[12C,p]13C for internal consistency control. We will discuss the advantages and challenges with the different methods in our setup as well as the potential for future tritium measurements.
[1] A.W. Kleyna, W. Koppers, N. Lopes Cardozoa, Vacuum 80 (2006) 1098
[2] D. Grambole, T. Wang, F. Herrmann, F. Eichhorn, Nucl. Instr. and Meth. B 210 (2003) 526
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